Downlighters that are adapted to be installed into ceiling and/or roof spaces are inherently at risk of compromising the integrity of the ceiling and/or roof space. They are generally installed into an aperture in the ceiling that has to be relatively wide to accommodate the downlighter assembly and thereby compromises the ability of the ceiling to contain a fire in a room or even a fire caused by the light fitting itself failing. In order to compensate against these increased risks, it is generally required that downlighters incorporate adaptations to improve their fire barrier capabilities and which generally include the provision of intumescent materials associated with the downlighter assembly and which expend in the heat of fire to occlude the openings defined by the downlighter.
Since downlights generate a substantial amount of heat in operation, it is generally necessary that they be provided with ventilation apertures. However, fire rating requires that any ventilation apertures be sealed off by the intumescent material in event of a fire. In operation it is important that the intumescent material is stable and not triggered by the high levels of heat generated in normal operation of the light but that in event of a fire it expands to reliably occlude the openings.
Normal measures to fire rate downlighters include, for example, provision of hoods or tents that seat over the downlighter assembly in the manner of a shroud and which effectively entomb the downlighter in event of a fire. See, for example, GB-2,270,936. More recently downlighter assemblies have been adapted to incorporate intumescent material more intimately associated with the downlighter itself and commonly mounted in immediate proximity to the casing of the downlighter at the rear end of the casing in order specifically to occlude ventilation apertures in the rear end of the casing. In general the intumescent material is applied as a sheet/layer that is laminated or sandwiched to the end wall of the lamp casing either internally or externally. However, the positioning of a layer of intumescent material at the end of a downlighter assembly may compromise the flow of air through the downlighter. This can cause excessive heat to build up during operation. This has at least two disadvantages. Firstly, bulb life may be significantly reduced and secondly, the intumescent material may be triggered to expand because of the excessive heat resulting from continuous running of the bulb. In order to avoid this, intumescent material which starts to expand at a higher temperature tends to be used. This makes the whole assembly less sensitive and slower to close up in the event of a fire. Further drawbacks of this prior art include that they need to be used only with aluminium reflector lamps, being incompatible for use with the popular dichroic reflector lamps since these latter direct the heat from the lamp rearwardly and which would cause excessive heat build up inside the casing reducing lamp life and risking premature activation of the intumescent material.
It is an object of the present invention to provide a fire rated downlighter arrangement that provides an alternative or improved arrangement for fire retardance.